This image shows changes in the target landing area for Curiosity, the rover of NASA's Mars Science Laboratory project. The larger ellipse was the target area prior to early June 2012, when the project revised it to the smaller ellipse centered nearer to the foot of Mount Sharp, inside Gale Crater. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

NASA has narrowed the target for its most advanced Mars rover, Curiosity, which will land on the Red Planet in August. The car-sized rover will arrive closer to its ultimate destination for science operations, but also closer to the foot of a mountain slope that poses a landing hazard.

"We're trimming the distance we'll have to drive after landing by almost half," said Pete Theisinger from NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "That could get us to the mountain months earlier."

It was possible to adjust landing plans because of increased confidence in precision landing technology aboard the Mars Science Laboratory (MSL) spacecraft, which is carrying the Curiosity rover. That spacecraft can aim closer without hitting Mount Sharp at the center of Gale Crater. Rock layers located in the mountain are the prime location for research with the rover.

Curiosity is scheduled to land at approximately 1:31 a.m. EDT August 6. Following checkout operations, Curiosity will begin a two-year study of whether the landing vicinity ever offered an environment favorable for microbial life.

The landing target ellipse had been approximately 12 miles (20 kilometers) wide and 16 miles (25km) long. Continuing analysis of the new landing system's capabilities has allowed mission planners to shrink the area to approximately 4 miles (7km) wide and 12 miles (20km) long, assuming winds and other atmospheric conditions are as predicted.

Even with the smaller ellipse, Curiosity will be able to touch down at a safe distance from steep slopes at the edge of Mount Sharp.

"We have been preparing for years for a successful landing by Curiosity, and all signs are good," said Dave Lavery from NASA. "However, landing on Mars always carries risks, so success is not guaranteed. Once on the ground, we'll proceed carefully. We have plenty of time since Curiosity is not as life-limited as the approximate 90-day missions like NASA’s Mars Exploration Rovers and the Phoenix lander.”

Since the spacecraft was launched in November 2011, engineers have continued testing and improving its landing software. MSL will use an upgraded version of flight software installed on its computers during the past two weeks. Additional upgrades for Mars surface operations will be sent to the rover about a week after landing.

Other preparations include upgrades to the rover's software and understanding effects of debris coming from the drill the rover will use to collect samples from rocks on Mars. Experiments at JPL indicate that Teflon from the drill could mix with the powdered samples. Testing will continue past landing with copies of the drill. The rover will deliver the samples to onboard instruments that can identify mineral and chemical ingredients.

"The material from the drill could complicate but will not prevent analysis of carbon content in rocks by one of the rover's 10 instruments. There are workarounds,” said John Grotzinger from the California Institute of Technology in Pasadena. "Organic carbon compounds in an environment are one prerequisite for life. We know meteorites deliver non-biological organic carbon to Mars, but not whether it persists near the surface. We will be checking for that and for other chemical and mineral clues about habitability."

Curiosity will be in good company as it nears landing. Two NASA Mars orbiters, along with a European Space Agency (ESA) orbiter, will be in position to listen to radio transmissions as MSL descends through Mars' atmosphere.